Method of rolling thin strips of metal



Jan. 3, 1928.

W. 5. KELLAR METHOD OF ROLLING THIN STRIPS OF METAL Filed July 10. 1925 Wren/Zr. M/////0/775 hZV/dr Patented Jan. 3, 1928.

UNITED STATES WILLIAM STANLEY KELLAR, OF CHICAGO,

PATENT.- OFFICE. 7

ILLINOIS, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF ROLLING THIN STRIPS OF METAL.

Application filed July 10,

This invention relates to a method of rolling thin strips of metal. It is well known that some of the more ductile metals can be rolled into the form of very thin sheets or strips. Examples of this type of work are to be had in the ordinary lead or tin foils. The usual methods which are employed to roll this type of material, however, cannot be employed with success when rolling the well known hardened aluminum alloys. This latter type of metal has been found of particular use in the production of vibrating discs for various types of intelligence transmission apparatus. When employed for this purpose it is essential that the alloy possess the maximum tensile strength and in addition it should be exceedingly thin in order to function with the required degree of efficiency. A thickness of .001 of an inch or less has been found to give decidedly good results,.but a strip of aluminum alloy of this thickness cannot be produced by ordinary simple rolling processes such as are employed to produce foil as referred to above, considerable difiiculty being encountered in producing hardened aluminum alloy strips having thicknesses substantially less than .020 of an inch.

The object of the present invention is to successfully roll aluminum alloys in strip form to, thicknesses of the order of .020 of an inch or less, while retaining the maximum tensile characteristics thereof.

In order to practice the invention it has been found necessary to continuously work the hardened aluminum alloy strip a plurality of times with an initial pressure which is gradually increased but which however decreases for a given setting of pressure medium as the reduction in the thickness of the strip occurs, it being also desirable to tension the strip before and after it leaves the pressure medium which has been found to aid materially in the reducing operation. According to one form of the present invention there is provided a pair of power driven rolls which are capable of. very accurate alignment with respect to each other and which maybe subjected to minute changes in pressure. Cooperating with the rolls to exert a certain tension on the aluminum alloy strip before it is subjected to pressure is a guide mechanism which extends-t0 the rolls and which has its forward end shaped to 1925. Serial No. 42,659.

conform to their contour. In order to facilitate the reduction in the thickness of the aluminum alloy strip it is held under tension as it emerges from the rolls and as it is wound on a take-up reel by a friction mechanism which serves to drive the take-up reel.

The invention will be more fully understood from the following description taken with the accompanying drawings, wherein Fig. 1 is a side elevation of a rolling mill embodying the mechanical features of the invention;

Fig. 2 is a fragmentary plan view of part of the mechanism shown in Fig. 1; A

Fig. 3 is a vertical section taken on the line of Fig. 2 showing details of the guide,

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 1 showing the clutch by means of which the strip is held under tension as it leaves the rolls.

- The method will be more fully understood after a descri tion of the apparatus with which it may be practiced.

Referring now to the accompanying drawings in which like numerals are employed to designate similar members throughout the several views, Fig. 1 shows schematically the main portions of a rolling mill comprrsin the usual frame designated by the numera 10 and a plurality of rollers 11, which are suitably'mounted in the frame. The rollers 11 are shaped with journals 12 on either end thereof which journals '12 are fitted in bearings 13 which are suitably secured in the main frame 10. The rollers 11 terminate at one end thereof (Fig. 2) in a pair of shafts 15 and 16 by means of which the rolls are driven from a suitable source of power (not shown). The rolls are positioned with respect to each other by means of adjusting screws 17 which engage each one of the bearings 13 and separating springs .18 positioned between the bearings and tending to keep the rollers separated.

The improved guide comprises a lower member 20 and an upper member 21 and the strip 22 which is being rolled is led between the top and bottom members 20 and 21 as indicated particularly in Fig. 3. The lower member is provided with upwardly extending side pieces 25 which serve to engage the member 21 and at the same timeprevent lateral movement of the metal strip 22 as it passes to the rolls. The guides should be constructed so that they will be only slightly wider than the finished strip. Where strips .020 of an inch in thickness are to be rolled to .001 .of an inch, one quarter inch allowancefor widening of the strip through rolling is sufficient. Any suitable means may be provided for forcing the members 20 and 21 together in order to regulate the tension which will be placed upon the strip 22 as it enters the rolls, but where very thin strips are being rolled having a thickness of the order of say .001 of an inch or less, if the guide members 20 and 21 are well oiled the surface tension between the strip 22 and the upper and lower guides is sufiicient for the purpose. The guide member comprising the upper and lower members described extends to the rolls, the ends of the two members closest to the rolls being shaped to conform to the contour thereof. By this means the thin metal strip is guided practically to the" very point of contact with the rolls and buckling or overlapping of the strip between the guides and the rolls is practically impossible. The metal strip 22 is fed between the guide members 20 and 21 in any suitable manner such as from a reel 26 which is mounted in a suitable way in an operative position with respect to the guide member.

The strip 22 is kept under tension after it leaves the rolls and as it is reeled onto suitable take-up means such as a reel 30. The apparatus by which the strip is maintained under tension is as follows: The reel 30 revolves with a shaft 31 which is driven by'a friction clutch indicated generally by the numeral 32. The shaft 31 is journaled in a bearing 29 which is supported by suit able means such as uprights 33, the entire take-up mechanism being secured to the main frame 10 and being mounted on a frame 34. secured to the frame 10. A clutch member 35 has keyed thereto a pulley 36 which is driven by a smaller pulley 37 through a shaft 38 leading to a suitable source of power (not shown), a belt 39 serving to communicate power from the smaller pulley 37 to the pulley 36. The clutch member 35 has integral therewith a plurality of discs 40 which frict-ionally engage a plurality of discs 42 and a disc member 48 slidably secured to a member 43.. Thelatter member is secured to .the shaft 31 in any suitable b manner such as by a pin 44: and serves to drive the shaft. A nut 45 on the member 43 serves to tension a spring 46 by means of which the friction between the discs referred to is regulated.

When rolling very thine hardened aluminum alloy strips with the equipment described the strips should be rolled aplurality of times with one setting of the rolls. When the rolls are brought closertogether the first passage of the strip therethrough causes the strip to be wrinkled along the.

reason has no space in which to buckle or.

overlap before coming in contact with the rolls. At each setting of the rolls the strip should be rolled until all of the wrinkles disappear and the sheet is perfectly flat,

even when not subjected to tension.

When the rolls have been set closer together and the strip is passed between them the latter offers a resistance to the rolls which causes the rolls in turn to exert a pressure on the strip. With each successive pass between the rolls, however, due to the gradual reduction ofthe cross sectional area of the strip, this resistance decreases and the pressure which is exerted by the rolls is decreased proportionately. When the strip has reached the thickness which corresponds to the true setting of the rolls there is therefor no further reduction upon passing the strip therebetween, and the rolls are accordingly reset and the rolling process continued until the strip is again the thickness indicated by the roll setting.

When rolling hardened aluminum alloy to thicknesses of the order of .001 particular attention must be paid to the lining up of the rolls. For instance if thestrip to be produced is to be .001 thick the rolls should be true to at least .0001 of an inch both as to parallelism and as to diameter. For example if the axes of both rolls are not in the same plane the strip will be torn. If, however, the axes of the rolls are in the same plane they must also be parallel in that plane or an arcuate strip will be produced. The two rolls should be of exactly the same diameter and both should be driven at exacltly the same speed to secure the best resu ts.

The highest degree of cleanliness in the guides and rolls must alsobe observed or the very thin strips will be porous and unfitted for the use referred to in the introductory paragraph. The oil employed should also e clean and free of suspended particles, 9. good grade of heavy mineral oil being the best when very thin strips are produced. Lard oil is a very good lubricator and may be employed advantageously where the strips to be produced are not thinner than .004 or .005 inch. Very thin strips, however, are apt to be porous if rolled with lard oil.

The invention is of particular advantage in producing strips of hardened aluminum alloys. which are suitable for the manufacture of vibrating discs for the use previously referred to. Material to be used for this purpose should have a tensile strength better than 75,000 pounds per uare inch. When producing1 teristic t e normal process for producing aluminum alloy strips can be em loyed until the strip is of the thickness of a out .020 of an inch. This normal process consists in casting a billet of proper chemical constitution and alternately annealing and cold rolling the billet until it is as thm as it can be conveniently rolled with the standard equipment. .The strip is then heated to about 930 F. and quenched according to the conventional practice and then immediately rolled according to the present invention to the final thickness desired. By employing the steps of the process described in the foregoing portion of the specification in this way, the finished stri. possesses the normal hardening obtained y cold rolling as well as the hardening produced by age hardening which is a phenomenon encountered after heat treating some metals consisting of a gradual hardenlng of the metal which continues in some cases for about four days. .Although the novelty in the invention is confined primarily to the 'final stages of the process wherein very thin strips are rolled the invention is not to be confined to these particular steps but is to be limited only by the scope of the appended claims.

What is claimed is:

1. The method of working aluminum alloy strips, whichconsists in guiding the strip to the very point of application of pressure, subjecting the strip to a gradually reduced pressure, increasing the pressure, and then again subjecting the strip to a adually reduced pressure until the strip is of the desired thickness.

2. The method of working aluminum alloy strips, which consists in guiding the strip to strips having t is tensile charac ting the rolls and finally rolling the strip a plurality of times with the new setting of the rolls to reduce the strip to the desired thinness.

4. The method of producing hardened aluminum alloy strips having high tensile strength. which consists in casting a billet of the alloy, alternately rolling and annealing the billet in a plurality of stages until a strip having a thickness of the order of .020 inch is produced, then heating and quenching the. strip and finally rolling the strip to produce a strip of smaller cross sectional area, this latter step comprising guiding the strip to the very point of application of pressure, maintaining the strip under tension and subjecting the strip a plurality of times at each increment of a gradually increased pressure.

5. The method of producin hardened aluminum alloy strips having aiigh tensile strength, which consists in subjecting the strip to a gradually reduced pressure, increasing the pressure, and then again subjecting the strip to a gradually reduced pressure until the strip is of the desired thickness.-

In witness whereof, I hereunto subscribe my name this 30th day of June A. D., 1925.

WILLIAM STANLEY KELLAR. 

